In the latest effort to mimic our organ development in the lab, Japanese scientists have grown a human-eye precursor in vitro.

The structure – an optic cup – contains layers of cells, including the light sensing photoreceptors in retinas. With this finding, doctors could one day be able to repair damaged eyes in the clinic. David Cyranoski reports for Nature News.

In their experiment, retinal precursor cells spontaneously formed a ball of tissue cells.

Then they bulged outwards to form a bubble called an eye vesicle.

That pliable structure then folded back on itself to form a pouch, creating the optic cup.

This has an outer wall and an inner wall with layers of retinal cells, including photoreceptors and the neurons that receive visual info from photoreceptors.

Until recently, biologists have grown embryonic stem cells into two-dimensional sheets. In the past 4 years, Sasai has used mouse embryonic stem cells to grow three-dimensional cerebral-cortex, pituitary-gland, and optic-cup tissue.

This latest effort marks the first time anyone has managed a similar feat using human cells.

Last month, a group at University College London showed that a transplant of stem-cell derived photoreceptors could rescue vision in mice – but the transplant involved only rod-shaped receptors, not cone-shaped ones, leaving images fuzzy.

With Sasai’s organically layered structure, integrated photoreceptor tissue could one day be transplanted. The developmental process could also be adapted to treat a particular disease, with tissue stocks created for transplant and frozen.

The cells in the optic cup are “pure,” according to Sasai, unlike those in two-dimensional aggregates, which may still contain embryonic stem cells – reducing concerns that transplants will develop cancerous growths or fragments of unrelated tissues. “It’s like pulling an apple from a tree. You wouldn’t expect iron to be growing inside,” Sasai says. “You’d have no more reason to expect bone to be growing in these eyes.”

Researchers have started transferring sheets of the retina from such optic cups into mice, with plans to do the same with monkeys by the end of the year.

Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York.
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